1. Field of the Invention
The present invention relates to an electron-emitting device used for a flat panel display, and a method of manufacturing the electron-emitting device, an electron source including the electron-emitting device, and an image display apparatus using the electron source.
2. Description of the Related Art
A surface conduction electron-emitting device is based on the phenomenon that a conductive film formed on an insulating substrate is supplied with a current in parallel to a surface of the conductive film, to emit electrons. Fundamentally, a pair of device electrodes are formed on the substrate. The conductive film is formed so as to connect the device electrodes to each other. A minute gap is provided in the conductive film to form a pair of conductive films. An operation called “activation” is performed to deposit a pair of carbon films in the gap and on portions of the conductive films which are close to the gap. The pair of carbon films have a minute gap and each of the carbon films is connected to corresponding one of the conductive films. When a predetermined voltage is applied between the device electrodes in the electron-emitting device, electrons are emitted from the vicinity of the gap between the conductive films and the vicinity of the gap between the carbon films.
Japanese Patent Application Laid-Open No. 2000-251628 discusses a structure in which the carbon films are deposited to extend from the vicinity of the gap between the conductive films to a portion of the substrate which is located outside the vicinity of the gap.
The extending portions of the carbon films are conductive, and accordingly there is an effect that a variation in potential of a surrounding surface of the insulating substrate is reduced. However, a sufficient gap cannot be provided between the extending portions of the pair of carbon films depending on formation conditions, and hence there is a case where end sections (sections apart from the conductive films) of the extending portions are connected to each other.
When the extending portions of the carbon films are connected to each other as described above, an ineffective current (leak current) flows between the device electrodes through the extending portions, and, as a result, there is a case where electron-emitting efficiency reduces. Long time driving or vacuum atmosphere reduction tends to cause discharge break-down. Depending on a material or surface state of the substrate on which the electron-emitting device is placed, the extending portions of the carbon films are likely to vary in shape, which tends to cause variations in electron-emitting characteristics of electron-emitting devices. The electron-emitting efficiency (η) is estimated as a ratio between a device current If flowing between the pair of device electrodes included in the electron-emitting device and an electron-emitting current Ie (current reaching the anode) and expressed by “η=Ie/If”.
A display using a large number of electron-emitting devices is required to have low power consumption and high luminance and obtain an image with high uniformity. Therefore, the electron-emitting device is required to have high efficiency and stably and uniformly obtain a large electron-emitting amount.